Phosphors (hereinafter referred to as “CASN phosphors”) with a crystal structure represented by the formula CaAlSIN3 are known as red phosphors which emit light with a wavelength greater than that of the light emitted from rare-earth element-activated sialon phosphors and which have high brightness (see Patent Documents 1 and 2).
Patent Document 1 discloses that an increase in the content of Eu, which is an activation element, reduces emission intensity because of concentration quenching.
Patent Document 2 discloses that the phosphors have been produced using different types of Eu-containing compounds.
Patent Document 1: Japanese Unexamined Patent Application Publication No. 2006-8721
Patent Document 2: Japanese Unexamined Patent Application Publication No. 2006-8948
Since there is an increasing demand for displays having a high NTSC ratio in recent years, CASN phosphors having a longer emission peak wavelength are increasingly demanded as compared to conventional ones. Therefore, the following method has been demanded: a method for producing a CASN phosphor which can be prevented from being reduced in emission peak intensity and which has a long emission peak wavelength.